The ORIGIN-FH Study

Inclusion Criteria - parent participant: * Individuals in the expectant partnership providing informed consent are at least 18 years of age. * Ability to understand and willingness to sign a written informed consent document. * Willingness to comply with all study procedures and be available for the duration of the study. * Expectant parent (currently pregnant with fetus ≥12 weeks gestation) where one or both partners have been diagnosed with possible or definite HoFH or HeFH based on Dutch Lipid Clinic Network (DLCN) or confirmed diagnosis from a healthcare provider. At minimum, at least one parent with HoFH or HeFH must be willing to consent to study participation. However, both parents will be invited to participate. * Parent(s) commit to using local laboratory services for infant blood samples, with mobile phlebotomy used as an alternative if available in their area. Inclusion Criteria - newborn participant: * Newborn does not have any congenital abnormalities or medical conditions that may interfere with collection of dried blood spot (DBS) specimen and newborn does not require admission to neonatal intensive care unit. Exclusion Criteria - parent and newborn participants: * Expectant partnership where neither partner meets diagnostic criteria for HeFH or HoFH. * Parent refuses consent for newborn's study participation. * Newborn has medical condition precluding DBS specimen collection, or a newborn's DBS specimen is not collected by 1 week of age. * Not suitable for study participation due to other reasons at the discretion of the investigators. * Parent and newborn live outside of the United States.